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Yak 15 for Rapier L2 motor

In 1945 Germany, Great Brittain and USA had jet fighters available, exceeding the types of planes used in USSR. In post war years it was not possible to buy the planes or get a licence. One of the first answers to such situation came from design bureau of A.S. Jakovlev. Their first jet was designed to be available in a short time and the production could use many of techniques verified in common fighters produced so far. Yak 15 was based on Yak 3. Piston engine was replaced by RD-10 engine with 9120N thrust hooked up on the front section of the fuselage and ending below the fuselage. Two cannons B-20 were placed above the engine, later replaced by NS-23. The first prototype flew on April 24th 1946, only 14 month after task was placed.

I drew the plan for this aircraft based on detailed information from my favourite book by Vaclav Němeček: Vojenská letadla 4, published by Naše vojsko, 1979 and using internet sources: http://www.airwar.ru/other/draw/yak15.html. Model is made of balsa, covered by modelspan.

Author: Jan Straka

Yak 15

Yak 15 for Rapier L2 motor

Building plan

Is available in PDF formt. One should carefully measure after the printing whether the plan size correspond with the wingspan given on the plan. Badly scaled printing would bring tears when found after building the whole model.

Plán Building plan - PDF (202 kB)

Building notes

Fuselage:

The first step is preparation of two trussed sides, glued directly on the plan covered with plastic foil. Torso of the fuselage is then made of the sides and cross bars. Then we add G former and halfformers H, I, J and K (all formers are carefully cut from 0.8mm balsa covered by paper). Put the keels pos. 1 and 2 into the formers, add formers B, C, D, E and F and further add keels pos.3. Do not glue yet ! The fuselage is designed so it can be put onto steel ruler and check the alignment. Add reinforcements pos. 4 and When everything is in place and checked, glue it all together with diluted glue. Stringers are cut from 1mm balsa and after gluing to fuselage sanded to 0.8mm. Motor section is is made of cut paper tube prepared on 18 mm dowel. Intake and outtake are made of light balsa. Finally I prepared transitions pos. 5. The first window on lower part of the fuselage behind the motor output should be filled with light balsa. Elevator and rudder is made of balsa sheet 0.8mm. Canopy is made from Durofol 0.2mm on balsa last.

Wing:

Is made of two halfs. Prepared parts are assembled without gluing in pin template on the plane. Then glued together with diluted glue.

Covering:

The fuselage is covered with rudder in place. The elevator is glued firmly after the trimming. Wings halves are glued to the fuselage after covering. Incidence angle and dihedral must be kept properly. The fillets are made from covering paper. Protection against motor exhaust high temperature is made of alu foil, whole lower part of the fuselage is covered.

Motor mount

is made of paper tube rolled directly on Rapier L2 motor. Mount is attached to the fuselage by 2x2 mm spar so the mount is not directly in contact with the fuselage.

Trimming

must be performed with empty rocket motor. I recommend to check model behavior after strong throw. I made a mistake with gentle flight at home to the bed. I set negative angle of the elevator and powered flights on the meadow were rather wild. The COG is below the wing main spar.

If you put bamboo pin into the front part, you can dart the model with rubber ring.

Photographs of the model

Jak 15 (built and photographed by: Jan Straka)

Formers installation...

Jak 15 (built and photographed by: Jan Straka)

The bones (built and...

Jak 15 (built and photographed by: Jan Straka)

The bones (built and...

Jak 15 (built and photographed by: Jan Straka)

The bones (built and...

Jak 15 (built and photographed by: Jan Straka)

The bones (built and...

Jak 15 (built and photographed by: Jan Straka)

Model prior to cover...

Jak 15 (built and photographed by: Jan Straka)

Model prior to cover...

Jak 15 (built and photographed by: Jan Straka)

Model prior to cover...

Jak 15 (built and photographed by: Jan Straka)

Motor mount, at the ...

Jak 15 (built and photographed by: Jan Straka)

Jak 15 finished (bu...

Jak 15 (built and photographed by: Jan Straka)

Jak 15 just prior t...

Jak 15 (built and photographed by: Jan Straka)

and view from the ot...

Jak 15 (built and photographed by: Jan Straka)

Take off preparation...

Jak 15 (built and photographed by: Jan Straka)

First starts - clear...

Jak 15 (built and photographed by: Jan Straka)

And here is the proo...

Jak 15 (built and photographed by: Jan Straka)

Art shot - searching...

Jak 15 (built and photographed by: Jan Straka)

This is not damage c...